Glenn Branch's picture

Falsifia-behe-lity on the Edge

Physical model of a bacterial flagellum

As a dog returneth to his vomit, I seem to be returning to, if not my folly, then Michael Behe’s folly. (I was going to try a pun here with “folly” and “falsifiability”—possibly involving “follysifiability”—but it was too much of a strain.) Previously, I was examining Behe’s arguments about the falsifiability of “intelligent design” and what he calls “Darwinism” in a 2001 paper entitled “The Modern Intelligent Design Hypothesis.” I argued (in “Falsifia-behe-lity”) that his attempt to turn the tables, by contending that “intelligent design” is but “Darwinism” is not falsifiable, fails. And then I argued (in “Falsifia-behe-lity Revisited”) that his accusation that his critics are trying to have their cake and eat it too, by arguing that “intelligent design” is both falsified and unfalsifiable, also fails. But those discussions concentrated just on that 2001 paper, so I decided to take a look at Behe’s two books to see what, if anything, he says about falsifiability there.

The term “falsifiability” doesn’t appear in the index of Darwin’s Black Box (1996), and as far as I can tell the word appears in the book only in a quotation from the decision in McLean v. Arkansas in a footnote: “Judge Overton, echoing Ruse, wrote of science that: ‘(1) It is guided by natural law; (2) It has to be explanatory by reference to natural law; (3) It is testable against the empirical world; (4) Its conclusions are tentative; i.e., are not necessarily the final word; and (5) It is falsifiable.’” Behe is citing Overton in the context of his discussion of Richard E. Dickerson’s advocacy of methodological naturalism, which he rephrases in terms of (1) and (2), so he doesn’t address the remaining three clauses. The discussion of Dickerson occurs in chapter 11, “Science, Philosophy, and Religion,” and while Behe anticipates and tries to disarm a number of criticisms of his position there, he doesn’t seem to consider the charge of unfalsifiability.

It seems likely, then, that Behe addressed the charge of unfalsifiability only in order to respond to his critics. There were a lot of critics, of course, and some of them were quite explicit in citing the unfalsifiability of Behe’s claims on behalf of “intelligent design” in their criticisms. Jerry Coyne, for one, leveled the charge, or a form of it at any rate, in his review in Nature of Darwin’s Black Box in 1996:

If one accepts Behe’s idea that both evolution and creation can operate together, and that the Designer’s goals are unfathomable, then one confronts an airtight theory that can’t be proved wrong. I can imagine evidence that would falsify evolution (a hominid fossil in the Precambrian would do nicely), but none that could falsify Behe’s composite theory. Even if, after immense effort, we are able to understand the evolution of a complex biochemical pathway, Behe could simply claim that evidence for design resides in the other unexplained pathways. Because will never explain everything, there will always be evidence for design. This regressive ad hoc creationism may seem clever, but it is certainly not science.

Coyne is not exactly hitting the nail on the head here (he conflates “intelligent design” with respect to a system and “intelligent design” in general; the latter is unfalsifiable in a way above and beyond the ways in which the former is unfalsifiable), but the presence of criticisms like these in leading scientific journals would naturally impel their recipient to try to respond, as Behe did in “The Modern Intelligent Design Hypothesis.”

In The Edge of Evolution (2007), Behe returns to the issue of falsifiability, writing, “Darwin and design hold opposite, firm expectations of what we should find when we examine a truly astronomical—a hundred billion billion—number of organisms. Up until recently, the magnitude of the problem precluded a definitive test. But now the results are in. Darwinism’s most basic prediction is falsified.” So “Darwinism” is falsifiable. Yet as far as Behe was concerned in 2001, “Darwinism” with respect to a system such as the bacterial flagellum (the poster organelle of the “intelligent design” movement, pictured above) is unfalsifiable, since “one would have to show the system could not have been formed by any of a potentially infinite number of possible unintelligent processes, which is effectively impossible to do.” Whence the discrepancy between Behe as of 2001 and Behe as of 2007? Did he change his mind, and if so, why?

One possibility, of course, would be that Behe didn’t change his mind at all with regard to the substantive issue; it’s just that his definitions of “Darwinism” and “intelligent design” differ—harmlessly if confusingly—between the two works. Let’s see. In “The Modern Intelligent Design Hypothesis,” Behe writes: “The claim of ID is that ‘No unintelligent process could produce this system.’ The claim of Darwinism is that ‘Some unintelligent process could produce this system.’” In The Edge of Evolution, Behe writes, “Darwinism implicitly entails the strong, broad, basic claim that, given enough chances, random mutation and natural selection can build the sorts of complex material we see in the cell. Intelligent design implicitly entails an equally strong, broad, basic prediction, that random mutation cannot do so.” These are similar, but they’re not quite identical: could the difference account for Behe’s volte-face?

The main difference is that “Darwinism” in 2001 refers to unintelligent processes but in 2007 it refers to random mutation and natural selection. In 2001, Behe thought that “Darwinism” was unfalsifiable because there was “a potentially infinite number of possible unintelligent processes”; in 2007, then, perhaps “Darwinism” is falsifiable because there is only one. There are a number of problems here, but the most significant problem is that the 2007 definition of “intelligent design” will no longer be what Behe wants. It will be the position that random mutation and natural selection can’t be the only process involved in producing the system in question. But, because there are plenty of natural processes involved in evolution other than random mutation and natural selection, establishing “intelligent design” in the 2007 sense isn’t enough to produce the desired consequence that intelligent design is actually involved in producing the system in question!

There are various ways that Behe might try to fix the 2007 definitions, but the most plausible ways of doing so will, I think, reinstate the multiplicity of processes on the “Darwinism” side of his attempted dichotomy that led him to conclude that “Darwinism” was unfalsifiable in 2001. So it’s hard to believe that the difference between the 2001 definitions and the 2007 definitions was responsible for his change of mind. Perhaps it is more plausible to surmise that Behe simply realized that his 2001 argument that “Darwinism” is unfalsifiable was irrevocably flawed and decided not to include it in The Edge of Evolution. I wouldn’t strenuously fault him for not acknowledging and explaining the change in his thinking: probably few readers of the book would know of or care about the 2001 paper, after all. But it would have been considerate of him to do so, for the benefit of any of his readers who are actually paying attention.